When you get this error:
Error Adding QuickBooks Estimate For Job: 1234 Windsor Crest Drive Guest Bath
Detail: Duplicate Document Number Error : You must specify a different number. This number has already been used.,
Message: Duplicate Document Number Error,
Code: 6140
This is because ContractorTools is attempting to create an estimate for a job with number "1234" (for example), and there is already a "document" in QuickBooks with number "1234". A "document" in QuickBooks can be either an estimate or an invoice.
To fix this, you will need to either change the job number of this job in ContractorTools, or change the estimate or invoice with this number in QuickBooks.
Once you have done this, then you need to clear the QuickBooks error(s) before attempting to sync again. Here’s how:
Go to ContractorTools and select "QuickBooks Sync" in the main menu.
Tap on "Sync Errors". This will take you to a list of the sync errors.
For each error, tap on it, then tap Clear.
Now go back to the QuickBooks Sync screen and tap "Sync Now".